Fails to load packages if both system and user data directories exist

[CaptainBeyondDS8]

When both a system (/usr/local/share/magicseteditor/data) and user (~/.magicseteditor/data) data directory exist, MSE fails to load packages. Specifically, it appears to be concatenating the user and system data paths together, as in /usr/local/share/magicseteditor/data/home/malacoda/.magicseteditor/data/magic.mse-game. I reproduced this on a fresh install of Ubuntu 20.04 using the latest HEAD commit as of this time (c07a8ff8f6692668c0c65a7e8f09fa9884634a4a)

The set up involves placing the MSE data itself in /usr/local/share/magicseteditor/data and templates in ~/.magicseteditor/data. Attached is a script that illustrates what I did to create this scenario: install-mse.txt

Steps to reproduce:

1. Build and install MSE binary to /usr/local/bin/magicseteditor
2. Copy MSE resource and data directories to /usr/local/share/magicseteditor/
3. Place Cajun-style templates in ~/.magicseteditor/data
4. Launch MSE
5. Click "New Set" button

Expected behavior: MSE shows available game types and card styles.

Actual behavior: Error message such as "Package not found: /usr/local/share/magicseteditor/data/home/malacoda/.magicseteditor/data/magic.mse-game".

Game type/card style selection is unusable.

strace logging confirms that MSE is indeed concatenating paths: strace.log

stat("/home/malacoda/.magicseteditor/data/home/malacoda/.magicseteditor/data/magic.mse-game", 0x7ffea7c6e610) = -1 ENOENT (No such file or directory)
stat("/home/malacoda/.magicseteditor/data/home/malacoda/.magicseteditor/data/magic.mse-game", 0x7ffea7c6e610) = -1 ENOENT (No such file or directory)
stat("/usr/local/share/magicseteditor/data/home/malacoda/.magicseteditor/data/magic.mse-game", 0x7ffea7c6e180) = -1 ENOENT (No such file or directory)
stat("/usr/local/share/magicseteditor/data/home/malacoda/.magicseteditor/data/magic.mse-game", 0x7ffea7c6e1e0) = -1 ENOENT (No such file or directory)
stat("/usr/local/share/magicseteditor/data/home/malacoda/.magicseteditor/data/magic.mse-game", 0x7ffea7c6e1e0) = -1 ENOENT (No such file or directory)

I tested this with the old 2.0.0 basic template set to confirm this was not somehow specific to the Cajun template set and found the same results.